In the past, an incandescent lamp and a halogen lamp are used as bulbs of a spotlight, a downlight, and the like. In recent years, a bulb (an LED lamp) including an LED (light-emitting diode) is being spread instead of the bulbs of this type.
In order to replace an existing bulb with the LED lamp, the LED lamp needs to include structure for enabling attachment to an existing luminaire. Therefore, the LED lamp includes a cap attachable to a socket of the existing luminaire and has size (in particular, size in the radial direction) for enabling the attachment to the existing luminaire.
The LED lamp can reduce power consumption. On the other hand, the LED lamp has a problem of aged deterioration in performance due to heat. Therefore, the LED lamp needs to include structure for thermal radiation in order to maintain light-emitting performance and durable life.
As the thermal radiation structure, for example, a thermal radiation fin is known. However, the LED lamp has the limitation in the size in the radial direction as explained above. Therefore, it is difficult to increase the diameter of the LED lamp to secure sufficient area of the thermal radiation fin.
Therefore, there is a demand for development of an LED lamp that can improve thermal radiation performance and a luminaire including the LED lamp.